The synthesis of iodobenzene starting from benzene and iodine is usually carried out in the liquid phase, in the presence of an oxidative agent; preferably the oxidative action is carried out by nitric acid (see Japanese Pat. No. 58/77830, U.S.S.R. Pat. No. 453392 and the article of Datta R. L. and Chatterjee N. R.: J. Am. Chem. Soc. 39, 437, 1917). Other oxidative agents may be used as well; none of them, however, has proved, hitherto, to be more efficient and convenient. For instance, iodic acid, sulfur trioxide and hydrogen peroxide were used (see Butler A. R.: J. Chem. Educ. 36, 508, 1971) and the aromatic iodination, catalyzed by metal halogenides, was reported as well (see Uemura S., Onoe A., Okano M, Bull. Chem. Soc. Jpn. 47, 147, 1974).
Recently Italian patent publication No. 19860 A/84, in the name of the Applicant, describes a process for the synthesis of aromatic iodo-substituted compounds starting from alkaline salts of aromatic acids, by reaction with iodine. In all the well known methods, the selectivities, with respect to iodine, are never higher than 90%; in a few methods use was made of expensive oxidative agents and in other methods one started from not easily available reactants.
Now we have found that the synthesis of iodobenzene can be carried out more conveniently according to the reaction: EQU 2C.sub.6 H.sub.6 +I.sub.2 +1/20.sub.2 .fwdarw.2C.sub.6 H.sub.5 I+H.sub.2 O (I)
using O.sub.2 as oxidative agent and a particular zeolite as catalyst.